Injection molds for containers, lids, and the like are typically of a fairly complex construction, comprising mold plates, leader pins, bushings, a hot runner system, an ejection system, a water and/or air cooling system, an opening and closing mechanism, and often a mold outrigger support system. Furthermore, such molds generally must be specifically manufactured to fit the desired molding press. Molding machines or presses come in various sizes and capacities, ranging typically from 200 tons to 700 tons.
Conventional molds may have a runner plate, which is a plate that typically holds a mold cavity on one side thereof, or a pair of mold cavities on opposed sides, and which has conduits that supply molten molding compound to the respective sprues of the mold cavities. Runner plates may be supported by outriggers, extending from corners of a rectangular runner plate in prior art designs in a direction parallel to a rectangular side thereof and integrally attached thereto. These outriggers are proportioned to rest upon tie bars of a particular molding press. In the prior art, the outriggers must be of a particular design to engage the particular tie bars of the desired molding press, since various molding presses of differing capacities and manufacture have tie bars of different spacing and size.
Thus, it is typically impractical to switch a mold from operation in one molding press to another molding press of different design, for example a molding press of larger capacity. In the prior art, the outriggers of the runner plate are likely to fail to engage the differently spaced tie bars of another design or size of molding press.
Furthermore, in the prior art molds where the runner plate carries a pair of mold cavities in back-to-back relation, it is conventional for leader pins to be present for lateral bracing of the mold as it opens and closes. Typically, one set of leader pins extends from one of the mold cores, secured in stationary manner on a mold core plate, which, in turn, is secured to a platen of the mold press. The leader pins from this first mold core plate extend outwardly through a peripheral aperture in the runner plate, being long enough to continue engaging the runner plate in the mold-open position, but not significantly longer than that. Then, the other mold core, on the other side of the runner plate and which engages the corresponding mold cavity on the other side of the runner plate, carries another set of leader pins through its mold core plate which are long enough to extend through apertures in the periphery of the runner plate as the entire structure is moved between open and closed positions, but likewise not significantly longer.
Thus, when such a prior art mold is in its open position, the leader pins are near their maximum position of extension, where only essentially the tips of the leader pins occupy the apertures in the runner plate. They would disengage from the runner plate if the mold were open much further, but the mold is designed not to open further. However, there is a weakness of lateral stability created by this structure, that has in the prior art been dealt with by the use of the outriggers described above for added lateral stability.
In accordance with this invention, a mold is provided having improved lateral stability, with the mold also exhibiting a universal characteristic of use, in that the very same mold may be run in a variety of molding presses. For example, preferred molds may be run in a variety of molding presses which range in capacity from 150 tons to 700 tons. This provides a significant and novel advantage, in that, in the prior art, it has typically been necessary to rebuild a mold with redesigned outriggers in order to switch its use from one press of one capacity or design to another press of a different capacity or design.
Further in accordance with this invention, one embodiment permits the elimination of the outrigger supports altogether, if that is desired.
Thus, a great improvement is provided with the mold of this invention.